Electrolytic printers are currently available which employ non-consumable electrodes. A non-consumable electrode is defined as one which does not participate in the chemical reaction which produces the resulting image. While these non-consumable electrodes do not participate in the reaction, they have been found to be subject to substantial wear.
U.S. Pat. No. 3,761,954 suggests that wear might be the result of corrosion due to arcing and other atmospheric conditions at the tip of the electrode. U.S. Pat. No. 3,761,954 goes on to suggest that iridium has been found to be an acceptable material for printing electrodes since it is a good conductor and also highly resistant to the corrosion that occurs at the tip of the electrode when it is in actual use.
U.S. Pat. No. 4,042,936 suggests the use of electrodes made from tungsten, iridium, silver, stainless steel or the like. U.S. Pat. No. 4,042,936 points out that one of the problems associated with electrolytic printing is wear of the electrodes and suggests that the problem may be overcome by employing a special printing medium.
While the noble metal oxides have been employed for electrode materials for the electrolysis of aqueous solutions containing alkaline metal halides, these solutions are not analogous to the solutions employed in electrolytic printing.
U.S. Pat. No. 4,100,050 suggests that for a highly alkaline liquor employed in electrolysis, the rate of consumption of noble metal electrodes is greater than that of the noble metal oxide electrodes. U.S. Pat. No. 4,100,050 goes on to report that the consumption rate is reduced by about an order of magnitude when a ruthenium electrode is replaced with a ruthenium oxide (RuO.sub.2) electrode. It should be pointed out that the liquors or solutions used for electrolysis are substantially more corrosive than those employed in printing operations.
The analogous electrolytic art which teaches the use of non-consumable electrodes for electrolytic printing does not indicate that the wear rate of the electrode is to a large extent controlled by the dissolution rate of the electrodes. Therefore, employing noble metal oxides for electrodes for electrolytic printers would not be an obvious way to alleviate the wear problem.